Al-based Ohmic reflectors with low leakage currents and high reflectance for p-GaN flip-chip processes

The authors report the improvement of InGaNGaN light-emitting diodes on Al reflectors, commonly used as n -type GaN contacts. A Cu-doped indium oxide (CIO) (5 nm) /indium tin oxide (ITO) (380 nm) interlayer was deposited and annealed at 500 °C, after which an Al (400 nm) Ti-W (30 nm) layer was sputtered on the ITO interlayer to reflect the light. The reflectance of CIOITOAlTi-W was ∼92% at 460 nm, higher than that of the popular NiAgPt scheme, and the forward voltage was 3.2-3.3 V, similar to that of the NiAgPt contact. Furthermore, the mean leakage current of CIOITOAlTi-W was 0.12 μA, much lower than 0.54 μA of NiAgPt at -5 V.